Melt butter in 1-quart saucepan over medium heat.,Cook leeks in butter about 3 minutes, stirring frequently, until softened; remove from heat.,Cut enough bread into 1-inch cubes to measure 5 cups.,______,Spread bread mixture in ungreased square baking dish, 8x8x2 inches.,Sprinkle with cheese.,Mix remaining ingredients; pour over cheese.,Cover tightly and refrigerate at least 4 hours but no longer than 24 hours.,Heat oven to 325F Uncover and bake 50 to 55 minutes or until knife inserted in center comes out clean.,Let stand 10 minutes before cutting.